1. Field of the Invention
The present invention relates to an image processor and image processing method.
2. Discussion of the Background
An inspected object such as a printed wiring board often includes a shape that often misjudged as a defect by a wiring pattern inspecting apparatus. Because of this a part containing the shape must not be a target of the inspection. A part of a hole connecting between layers, such as a through hole and a photo via hole (hereinafter referred to as xe2x80x9ca via holexe2x80x9d) is correspondent to the shape. For example, Japanese Patent Laid-Open No. 6-294626 bulletin disclosed a conventional wiring pattern inspecting apparatus comprising a quality inspection of a wiring pattern by extracting a true defect data based on a pattern image got by capturing an inspected object, and a hole mask image made separately. That is, among defect candidate data in the pattern image, a data not correspond with the hole mask image is a true defect data. This hole mask image is made by contrasting a hole measurement signal showing a part comprising a shape considered to be a through hole in a pattern image and a hole recognition effective signal provided from a specification of the inspected object. The contents of Japanese Patent Laid-Open No. 6-294626 are incorporated herein by reference in their entirety.
In this conventional technique, the extraction of the hole measurement signal from the pattern image is done as follows. As shown in FIG. 11, a number that a black pixel continues is counted on every eight directions of N, NE, E, SE, S, SW, W, NW from a point where four black pixels are gathered in a binarized pattern image. And the hole measurement signal is turned on about each pixel of the point if there is a number that the black pixel continues in a predetermined range (an upper limit value and a lower limit value of a number of pixel corresponding to a through hole radius) about each direction.
However, the conventional wiring pattern inspecting apparatus includes a problem explained in the following. A penetration hole such as a through hole can be coped with, but a non-through hole such as a blind via hole formed by a laser process or a photo via hole cannot. The cause is included in a difference on a binarized pattern image with a through hole and a photo via hole. A through hole is a penetration hole, and then if an internal pixel of the through hole is binarized, the pixel becomes black by all means. Because of this, on a binarized pattern image, the through hole appears as an approximately circular mass of black pixels as shown in FIG. 3. Therefore the through hole can be recognized by a measurement such as FIG. 11. Still, in FIG. 3, xe2x80x9c0xe2x80x9d shows a black level with a white level xe2x80x9c1xe2x80x9d(the same in FIG. 4, FIG. 13 and so forth).
On the contrary, as for a photo via hole and so on, an internal pixel does not always become black because base copper in the hole shines dully. So, as shown in FIG. 4, on a binarized pattern image, the photo via hole is recognized as a black pixel area of a distorted shape. There can be a part T that has only one pixel width in the black pixel area. If the measurement such as FIG. 11 is done with the part T, as shown in FIG. 12, a count start pixel on a certain direction (N, NE, NW) does not become black. Then, a hole measurement signal cannot be turned on about this part T. Therefore, the measurement such as FIG. 11 cannot be done on this part T. Still, in FIG. 12, sign xe2x80x9cxxe2x80x9d referred right of a direction sign shows that the count on the direction cannot be done. And, a number in parentheses on right of a direction sign shows a count number on the direction (the same in FIG. 13).
Although, by paying attention to an area except for the part T in a shape shown in FIG. 4, the measurement such as FIG. 1 looks possible, the number is not in the predetermined range. A case that the measurement such as FIG. 11 is really possible is extremely limited. Therefore, by a hole mask image of the conventional technique, the coat-ability of a photo via hole is bad, because an appropriate hole mask image can not be made. As a result in a case of an inspection of a wiring pattern, a lot of false signal occurs, and then the inspecting apparatus is inconvenience.
By the way, in FIG. 12, a value of a numerical sum of a black pixel on each direction becomes, even the part T in FIG. 4, a positive finite value (3+1+1+1+2=8). Therefore, by setting a constant upper limit value in the value of the sum, the measurement such as FIG. 11 can recognize the part T. However, when the measurement is done with a parallel pattern consisting of a conductor spacing Z of width in unison with a diameter of a photo via hole as shown in FIG. 13, the value of the sum (4+4+4=12) can become equal to or less than the upper limit value. This means a place that is not a photo via hole is recognized a place that is a photo via hole. If there is a hole recognition effective signal near the parallel pattern, an unnecessary hole mask is generated, and then the reliability of the inspection is dropped. Although, it is conceivable that the affine transformation (a parallel transfer, magnification revision, a turn transfer) is made on the pattern image for matching, the inspection tact time increases largely.
According to one aspect of the invention, an image processor includes a pattern image making unit, a judgment unit, a recognition area making unit, a processing candidate authorization unit and a processing image making unit. The pattern image making unit is for making a pattern image formed from pixel data obtained by capturing a pattern of an object. The judgment means is for counting, with respect to pixels included in the pattern image and in a plural directions from a selected pixel among the pixels, a number of same kind of pixels which consecutively continues from the selected pixel, and for determining in the plural directions whether the number is larger than a reference value. The recognition area making unit is for producing a processing recognition area effective signal that shows a range in which an area to be processed exists with respect to the object. The processing candidate authorization unit is for determining whether the selected pixel is a processing candidate pixel based on a determination of the judgment unit. The processing image making unit is for making processing image by comparing the processing candidate pixel and the processing recognition area effective signal.
According to another aspect of the invention, an image processor includes a pattern image making unit, a diameter judging unit, a mask recognition area making unit, a candidate authorization unit, a mask making unit and an inspecting unit. The pattern image making unit is for making a pattern image formed from pixel data obtained by capturing a wiring pattern of an object to be inspected. The diameter judging unit is for counting, with respect to pixels included in the pattern image and in a plural directions from a selected pixel among the pixels, a number of same kind of pixels which consecutively continues from the selected pixel, and for determining in the plural directions whether the number is larger than a reference value. The mask recognition area making unit is for producing a mask recognition effective signal that shows a range in which an area which is outside an inspection area exists with respect to the object. The mask candidate authorization unit is for determining whether the selected pixel is a mask candidate pixel based on a determination of the diameter judging unit. The mask making unit is for making a mask image by comparing the mask candidate pixel and the a mask recognition effective signal. The inspecting unit is for extracting a defect shape from a part of the pattern image except for the mask image.
According to yet another aspect of the invention, an image processing method includes making a pattern image formed from pixel data obtained by capturing a pattern of an object. With respect to pixels included in the pattern image and in a plural directions from a selected pixel among the pixels, a number of same kind of pixels which consecutively continues from the selected pixel is counted. In the plural directions, whether the number is larger than a reference value is determined. A processing recognition area effective signal that shows a range in which an area to be processed exists with respect to said object is produced. Whether the selected pixel is a processing candidate pixel is determined based on a determination whether the number is larger than a reference value. A processing image is made by comparing the processing candidate pixel and the processing recognition area effective signal.
At first, the wiring pattern inspecting apparatus captures a wiring pattern of an inspected object, and makes a pattern image consisting of pixel data got by capturing the wiring pattern. In the case the pixel data are binarized, each pixel in the pattern image is either of a black pixel or a white pixel. Generally, a pixel on a wiring pattern is a white pixel, and a pixel between patterns is a black pixel. And every pixel in a via hole is a black pixel ideally. However, a black pixel group in the via hole can be distorted really, because one part becomes a white pixel for variations of luminosity values before the binarization. Operations until this step is done by a pattern image making means.
Next, about each pixel in the pattern image, a diameter judgment is done by a diameter judging means. The diameter judgment is done as follows. The number that a black pixel continues is counted from a selected one pixel as a starting point on each direction of a plural number (4, 8, 12, 16 directions and so forth). That is, a measurement start pixel of an each direction is one point of a pixel as shown in FIG. 1. At this point the present invention differs from the conventional technique that a measurement start pixel is not always one point such as FIG. 11. Therefore, the counted number becomes 0 or a natural number. And then, the selected pixel is judged as following. When the counted number is a natural number of less than or equal to a predetermined value (an upper limit value), the direction is judged to be good. On the contrary, when the counted number is 0 or greater than the predetermined value, the direction is judged to be no-good. These processes are the diameter judgment, and done about each pixel in the pattern image.
Still, the upper limit value is a value corresponding to a size of an inspection outside area such as a via hole, but the value may not be the same about all directions. The reason is because the upper limit value may be different in a direction corresponding with X direction or Y direction and another diagonal direction in the pattern image. And the reason is because a shape in itself of the inspection outside area may not be always circular. In addition, the counting on each direction may be stopped at a point when the counted number exceeds the upper limit value. So, the counting is not necessary to be continued till a point where a continuation of a black pixel breaks off.
In this wiring pattern inspecting apparatus, a mask recognition area making means makes a mask recognition effective signal in parallel with a work of the diameter judgment. The mask recognition effective signal shows a range that there can be an inspecting outside area in an inspected object. The making processes are as follows. A standard position where there is an inspecting outside area such as a via hole in an inspected object has been input into the wiring pattern inspecting apparatus separately. The standard position may be input from a design data of the inspected object, or may be input from a measurement result of a measurement standard board that is only formed such as a via hole. On a real inspected object, the mask recognition effective signal is usually made by expanding to a moderate width because a position of an inspecting outside area slips a little off from the standard position by reason of a dispersion of an individual. A coefficient of the expanding time is determined by such as a precision described for the inspected object.
A result of the diameter judgment is sent to a mask candidate authorization means, and then authorized the selected pixel to a mask candidate pixel or not. Preferably this authorization is done as follows. A number of a direction that the judgment result is good is counted. Then, the number of a direction is compared with a predetermined threshold, and then if the number is more than or equal to the threshold, the selected pixel is authorized to a mask candidate pixel. When the threshold is a total number of the direction, the selected pixel authorized as a mask candidate pixel is a pixel in an area where a black pixel exists only in a diameter corresponding to the upper limit value. A black pixel in a via hole is the example. A pixel on a wiring pattern does not become a mask candidate pixel because the pixel is white. In addition, usually, a pixel between patterns does not become a mask candidate pixel because the pixel continues for long distance and so does not fit in a diameter corresponding to the upper limit value, even if the pixel is black. At this point, a defect based on a pinhole becomes a mask candidate pixel, but the defect is removed later.
The work described above is done about every black pixel in the pattern image. By the work, a mask candidate pixel is become, among black pixels, by a pixel in an inspecting outside area such as a via hole and by a pixel to be caused by a defect such as a pinhole.
In usual case, a predetermined threshold compared with a number of a direction is the same as a total number of the direction (4, 8, 12, 16 directions and so forth). The reason is as follows. The number that a black pixel continues should be within the upper limit value because an inspecting outside area such as a via hole is surrounded by a land of a wiring pattern usually. Therefore, even if the number is counted into any direction, the counting faces with a white pixel of a land by all means. If a black pixel continues for a long distance that exceeds the upper limit value on a certain direction, usual it is not a via hole and so on but a part between patterns.
But, this may not be always so. By a precision prescribed for an inspected object, there is a case that to some extent broken out in a land of a circumference of a via hole is permitted. In that case, the number that a black pixel continues on a direction going through the broken out part may be greater than the upper limit value. To authorize this selected pixel to a mask candidate pixel, the threshold must be turned into a few values than the total number of a direction. To be able to cope in case of both, it is preferable the threshold is made to be varying and includes the total number of a direction in the variable range.
However, the broken out part is usually only one place in a circumference of one via hole, and a remainder of the land should continue. Because a broken out of a land is occurs for an adjustment accuracy of a center position with a via hole and a land. Therefore, if the threshold turned into a few values than the total number of a direction, it is preferable to authorize a selected pixel to a mask candidate pixel only in a case that a number that a direction of that counted number is less than or equal to the upper limit value continues is equal to or more than the threshold value.
After the mask candidate pixel and the mask recognition effective signal is prepared, a mask making means compares them, and then makes a mask image. That is, the mask image is made of an extracted pixel that is a mask candidate pixel corresponding with the mask recognition effective signal. By this, a pixel in an inspection outside area such as a via hole among mask candidate pixels is removed besides . A pixel to be caused by a defect of a pinhole and so on is cut off here, so the pixel is not masked. When a mask candidate pixel corresponding with a mask recognition effective signal is extracted, a mask image can be made of only the pixel itself or can be made of pixels multiplied the pixel by some magnification. In this way, all black pixels in a binarized pattern image are just covered by the mask image.
After the mask image is made, an inspecting means does a last inspection. The inspecting means extracts a defect shape from a part except a part of the mask image among the pattern image. In a part of the mask image, even if a defect shape is inspected, it is ignored because it is caused by a via hole. At this point, the mask image made by the mask making means is just size, so reliability of an inspection in a vicinity of an inspecting outside area such as a via hole is not lost, and besides, the occurrence of a false signal is prevented.